This application proposes three experimental programs on human pitch perception: I. The pitch shift caused by a change in intensity is measured over a narrow frequency range and compared with threshold microstructure revealed by the audiogram. II. The pitch of a broad band noise with a sharp spectral edge is studied for different intensities, different edge frequencies and different edge shapes. III. The pitch of a dichotic noise with an interaural phase discontinuity of 180 degrees is studied for different frequencies and shapes of the discontinuity and for various interaural intensity differences. The same dichotic noise is used as a masker in experiments on direct masking and forward masking of a sine tone. The results of the three experimental programs are analyzed in terms of models of neural excitation patterns in the auditory system, including idiosyncratic variation of these patterns, and model processes for the extraction of pitch from the patterns. The experiments and the theoretical modeling will provide new knowledge about frequency analysis in the human auditory system and will have significant implications for clinical problems of current interest.